The unauthorized removal of articles such as that of taking books from libraries without checking them out is an ever-increasing problem, both in general societal terms and in terms of expense to the taxpayer and impairment of the information services provided by public libraries. In addition, there have been several noted recent instances of theft of relatively rare and valuable books from libraries. With limited resources, libraries cannot afford to lose any books, much less books that are essentially irreplaceable. In the commercial setting, retail stores have an obvious requirement to control shoplifting of expensive inventory such as designer clothing, prerecorded video movies, drugs, etc., which, of necessity, are displayed openly and are accessible to both the bona fide patron/customer and the would-be shoplifter.
Electronic article surveillance (EAS) systems for controlling pilferage, especially the unauthorized taking of books from libraries and book stores, are well known. One type of such EAS system employs ferromagnetic markers attached to the article. If the article is to be permanently marked to control its passage, a single-status, non-deactivatable marker will be used.
Alternatively, if the article is intended for authorized removal, a deactivatable, dual-status marker will be used. In the latter event, if the marker is not deactivated when the article is properly removed, the marker will be detected as the article is passed through the interrogation zone of the EAS system. A single status marker would also be so detected. More particularly, the interrogation zone is established by spaced apart detection panels placed across the exits. The panels include field coils for producing an alternating magnetic field across the exits and detector coils for detecting the passage of a marker between the panels.
It is also known to provide means for thwarting the counterfeiting of security or copyright-protected articles by marking such articles with non-removable labels containing indicia not visible via ordinary inspection and/or which is not reproducible except with sophisticated manufacturing equipment. One such technique utilizes labels containing retroreflective indicia visible only via hand-held retroreflective viewers. See, for example, U.S. Pat. No. 4,099,238 (Cook et al.).
Furthermore, it is also known to use optically detectable identification labels, such as the ubiquitous UPC product identification/price codes, to identify articles and to conceal such labels below transparent security layers.